U.S. patent application number 11/785095 was filed with the patent office on 2008-07-03 for method of producing copper nanoparticles and copper nanoparticles produced thereby.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Jae-Woo Joung, Young-II Lee, Young-Soo Oh.
Application Number | 20080157029 11/785095 |
Document ID | / |
Family ID | 38998399 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080157029 |
Kind Code |
A1 |
Lee; Young-II ; et
al. |
July 3, 2008 |
Method of producing copper nanoparticles and copper nanoparticles
produced thereby
Abstract
The present invention relates to a method of producing copper
nanoparticles, in particular to, a method of producing copper
nanoparticles, including: preparing a first solution including a
polar solvent, a dispersing agent and one or more reducing agents
selected from the group consisting of sodium
hypophosphates(NaH.sub.2PO.sub.2), hydrazine(N.sub.2H.sub.4),
hydrochloride and sodium borohydride(NaBH.sub.4) and heating the
solution; preparing a second solution including a polar solvent and
a copper precursor and heating the solution; and injecting the
heated second solution into the heated first solution at a time and
mixing each other. According to the present invention, copper
nanoparticles which are fine and uniform can be produced simply,
and thus the method is useful in mass production of copper
nanoparticles.
Inventors: |
Lee; Young-II; (Anyang-si,
KR) ; Oh; Young-Soo; (Seongnam-si, KR) ;
Joung; Jae-Woo; (Suwon-si, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700, 1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon
KR
|
Family ID: |
38998399 |
Appl. No.: |
11/785095 |
Filed: |
April 13, 2007 |
Current U.S.
Class: |
252/512 ;
420/469; 75/370; 977/773; 977/810 |
Current CPC
Class: |
B82Y 30/00 20130101;
B22F 9/24 20130101; C22C 9/00 20130101; Y02P 10/236 20151101; B22F
1/0018 20130101; H01B 1/026 20130101; Y02P 10/20 20151101; C22B
15/0089 20130101 |
Class at
Publication: |
252/512 ;
420/469; 977/773; 977/810; 75/370 |
International
Class: |
H01B 1/02 20060101
H01B001/02; C22C 9/00 20060101 C22C009/00; B22F 9/16 20060101
B22F009/16; B32B 15/02 20060101 B32B015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2006 |
KR |
10-2006-0064501 |
Claims
1. A method of producing metal nanoparticles, comprising: preparing
a first solution including a polar solvent, a dispersing agent and
one or more reducing agents selected from the group consisting of
sodium hypophosphates(NaH.sub.2PO.sub.2),
hydrazine(N.sub.2H.sub.4), hydrochloride and sodium
borohydride(NaBH.sub.4) and heating the solution; preparing a
second solution including a polar solvent and a copper precursor
and heating the solution; and injecting the second solution into
the first solution at a time and mixing each other.
2. The method of claim 1, wherein the polar solvent is one or more
selected from the group consisting of a polyol, water and an
alcohol.
3. The method of claim 2, wherein the polyol is one or more
selected from the group consisting of ethylene glycol, diethylene
glycol, triethylene glycol, polyethylene glycol and the mixtures
thereof.
4. The method of claim 1, wherein 2 to 6 moles of the reducing
agent are included in the first solution based to 1 mole of the
copper precursor.
5. The method of claim 1, wherein the dispersing agent is one or
more selected from the group consisting of polyvinylpyrrolidone
(PVP), cetyltrimethylammonium bromide (CTAB), sodium dodecyl
sulfate (SDS) and sodium carboxymethyl cellulose (Na-CMC).
6. The method of claim 1, wherein 1 to 20 moles of the dispersing
agent are included in the first solution based to 1 mole of the
copper precursor.
7. The method of claim 1, wherein the copper precursor is one or
more selected from the group consisting of CuSO.sub.4, CuCl.sub.2,
Cu(NO.sub.3).sub.2 and (CH.sub.3COO).sub.2Cu.
8. The method of claim 1, wherein the copper precursor is included
in the second solution at the concentration of 0.001 to 1 mole.
9. The method of claim 1, wherein the heating temperature is 70 to
120.degree..
10. The method of claim 1, wherein the injecting and mixing step is
performed for 2 to 10 minutes.
11. Copper nanoparticles, produced by a method comprising:
preparing a first solution including a polar solvent, a dispersing
agent and one or more reducing agents selected from the group
consisting of sodium hypophosphates(NaH.sub.2PO.sub.2),
hydrazine(N.sub.2H.sub.4), hydrochloride and sodium
borohydride(NaBH.sub.4) and heating the solution; preparing a
second solution including a polar solvent and a copper precursor
and heating the solution; and injecting the heated second solution
into the heated first solution at a time and mixing each other.
12. Conductive ink including the copper nanoparticles of claim 11.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2006-0064501 filed on Jul. 10, 2006, the contents
of which are incorporated here by reference in their entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a method of producing
copper nanoparticles having a uniform particle size and an
excellent dispersibility from copper ions in an aqueous
solution.
[0004] 2. Description of the Related Art
[0005] Recently, demands for a metal patterning of a thin film
through ink jet or microwiring formation on a substrate have been
increased according to a tendency of miniaturization and high
densification of electronic parts.
[0006] In order to implement this, it is required that a conductive
ink should be made from copper particles of nano-size which shows
an excellent dispersibility, a uniform shape and a narrow
distribution of particles.
[0007] There are various conventional methods of producing metal
nanoparticles, such as mechanical grinding method, co-precipitation
method, spray, sol-gel method, electrodeposition and micro emulsion
method. However, it is impossible to control size, shape and size
distribution of particles in the co-precipitation method. Also, it
is difficult to produce metal particles in mass production and
production cost is high in the electrodeposition and sol-gel
methods. In micro emulsion method, the size, shape and size
distribution of particles produced are easy to control, but it is
not suitable for practical use since the manufacturing process is
complicated.
[0008] Recently, a try to manufacture copper micro-powder using the
wet reduction process has been made. Here, a partial reduction
method using hydrazine was particularly provided as a proper means
for manufacturing copper particles having a particle size of about
0.1-100 .mu.m.
[0009] Japanese patent publication No. 1990-294414 provided a
method of producing copper particles including adding an alkali
hydroxide and a reducing sugar to a copper salt solution under the
presence of one or more compounds selected from the group
consisting of amino acid, the salts thereof, ammonia, ammonium
salts, organic amine and dimethyl glyoxime; and precipitating the
cuprous oxide particles; and subsequently reducing the copper oxide
particles with hydrazine.
[0010] In addition, Korean Patent publication No. 2005-3169
provided a method of producing copper particles, comprising making
an aqueous solution of copper salt complex by mixing an aqueous
solution of a copper salt with ammonia solution; and reducing the
aqueous solution of copper salt complex with ascorbic acid to make
copper powder, wherein surfactant is added to control the nucleus
size and growth of a copper particle for producing copper particles
of 0.3-4 .mu.m.
[0011] Further, Korean Patent Publication No. 2004-37824 provided a
method of producing ultra fine copper powder including adding NaOH
and hydrazine appropriately to aqueous solution of copper chloride
to make intermediate and complex; and making finally copper
particles of about 100 nm by wet reduction process.
[0012] Copper particles produced according to the methods provided
by the mentioned above were characterized by a feature that the
distribution of a particle size is to be small or the particle size
is to be uniform, but eventually they have shown wide distribution
of particle size due to difficulties in controlling the nucleation
and growth of copper particles. Moreover, they neither provided a
method of producing small and uniform particles of less than 100
nm, nor solved various problems in mass production of particles
economically.
SUMMARY
[0013] The present invention provides a method of producing copper
nanoparticles having a narrow distribution of particle size and an
excellent dispersibility by employing an appropriate dispersing
agent and a reducing agent in the conventional wet reduction
process.
[0014] Also, the present invention provides copper nanoparticles
produced by the method.
[0015] Further, the present invention provides conductive ink
including copper nanoparticles produced by the method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] These and/or other aspects and advantages of the present
invention will become apparent and more readily appreciated from
the following description of the embodiments, taken in conjunction
with the accompanying drawings of which:
[0017] FIG. 1 is a photograph representing powder of copper
nanoparticles produced according to an embodiment of the
invention.
[0018] FIG. 2a is a TEM image of copper nanoparticles produced
according to an embodiment of the invention.
[0019] FIG. 2b is a SEM image of copper nanoparticles produced
according to an embodiment of the invention.
[0020] FIG. 3 is a graph representing XRD analysis of copper
nanoparticles produced according to an embodiment of the
invention.
[0021] FIG. 4 is a graph representing TGA analysis of copper
nanoparticles produced according to an embodiment of the
invention.
DETAILED DESCRIPTION
[0022] One aspect of the present invention may provide a method of
producing copper nanoparticles, comprising:
[0023] preparing a first solution including a polar solvent, a
dispersing agent and one or more reducing agents selected from the
group consisting of sodium hypophosphates(NaH.sub.2PO.sub.2),
hydrazine(N.sub.2H.sub.4), hydrochloride and sodium
borohydride(NaBH.sub.4) and heating the solution;
[0024] preparing a second solution including a polar solvent and a
copper precursor and heating the solution; and
[0025] injecting the second solution into the first solution at a
time and mixing each other.
[0026] Another aspect of the present invention may provide copper
nanoparticles produced by the method.
[0027] Further, another aspect of the present invention may provide
conductive ink including the copper nanoparticles produced by the
method.
[0028] Hereinafter, the method of producing metal nanoparticles and
the metal nanoparticles thus produced according to the present
invention will be described in detail, taken in conjunction with
the accompanying drawings.
[0029] One aspect of the present invention may provide a method of
producing metal nanoparticles, including:
[0030] preparing a first solution including a polar solvent, a
dispersing agent and one or more reducing agents selected from the
group consisting of sodium hypophosphates(NaH.sub.2PO.sub.2),
hydrazine(N.sub.2H.sub.4), hydrochloride and sodium
borohydride(NaBH.sub.4) and heating the solution;
[0031] preparing a second solution including a polar solvent and a
copper precursor and heating the solution; and
[0032] injecting the second solution into the first solution at a
time and mixing each other.
[0033] In the present invention, an aqueous solution of copper
salts (a second solution) is made from a copper precursor, heated
to reaction temperature and then injected into an aqueous solution
including a dispersing agent and a reducing agent (a first
solution) at the same temperature as the reaction temperature
through a hot injection at a time, which is different from the
conventional wet reduction process. Using this method, the uniform
nucleation could be induced within short time and thus small copper
nanoparticles having a size of 20-50 nm can be manufactured in a
water based solvent system.
[0034] Here, the solvent for preparing the first solution and the
second solution may be a polar solvent including a polyol, water
and an alcohol. The solvent may be at least one selected from the
group consisting of ethylene glycol, diethylene glycol,
triethyleneglycol, polyethylene glycol and the mixtures thereof,
preferably ethylene glycol.
[0035] The reducing agent included in the first solution plays a
role of reducing a copper ion in the solution to a copper and may
be sodium hypophosphates. In an embodiment of the invention, sodium
hypophosphates induced a stable reduction reaction and resulted in
improvement in production yield of copper nanoparticles.
[0036] According to the present invention, 2 to 6 moles of the
reducing agent may be used based to 1 mole of copper salts. When
less than 2 moles of the reducing agent is used, complete reduction
of copper ions is not accomplished. On the other hand, it is
uneconomical and causes excess production of side products to add
more than 6 moles of the reducing agent since it is an excess
amount required in 100% reduction of copper ions.
[0037] The dispersing agent included in the first solution may be
one or more compounds selected from the group consisting of PVP
(Polyvinylpyrrolidone), CTAB (Cetyltrimethylammonium bromide), SDS
(Sodium dodecyl sulfate) and Na-CMC (Sodium carboxymethyl
cellulose), preferably PVP having molecular weight of 40,000 or
more.
[0038] A polymeric dispersing agent, PVP can control the size and
uniformity of the particles produced, prevente particles from
coagulating in a water based solvent, and provide great
dispersibility.
[0039] According to the present invention, 1 to 20 moles of the
dispersing agent may be used based to 1 mole of copper salts. When
less than 1 mole of the dispersing agent is used, it is difficult
to produce nanoparticles of a uniform size since the effect of
controlling copper nanoparticles is reduced. When more than 20
moles of the dispersing agent are used, it is difficult to react
uniformly since an excess amount of the dispersing agent causes
rising in viscosity and the resulting problem of agitation.
Moreover, a great amount of solvent is required to remove
by-products and residual organic compounds, which is
uneconomical.
[0040] The copper precursor may be one or more water soluble copper
salts selected from the group consisting of CuSO.sub.4, CuCl.sub.2,
Cu(NO.sub.3).sub.2 and (CH.sub.3COO).sub.2Cu, preferably,
CuSO.sub.4. Here, the copper precursor may be included at the
concentration of 0.001-1 mole in the second solution.
[0041] In the meantime, the first solution and the second solution
prepared according to the method of the invention may be heated to
and maintained at 70 to 120.degree. C. When it is over 120.degree.
C., the stability of the solution is reduced and the particles
being produced are not uniform since the subsequent reaction
progresses too fast. When it is below 70.degree. C., the reduction
reaction does not occur properly.
[0042] In the injection step, the second solution heated is
injected into the first solution heated through a hot injection,
and copper nanoparticles of 20-50 nm are produced. In this step,
additional heating process is not required. The reaction time may
be 2 to 10 minutes. When it is shorter than 2 minutes, the
reduction reaction is not achieved enough, and when it is longer
than 10 minutes, it is difficult to control the size of particles
produced uniformly due to overgrowth of a particle.
[0043] When the reaction completes, it may be stopped by cooling
quickly using cold distilled water to prevent overgrowth of
particles, and the copper particles produced can be separated using
a centrifuge. Then, the copper nanoparticles separated may be
washed with acetone and distilled water to remove by-products and
remaining organic compounds and dried at 50.degree. C. for 3 hours
in a vacuum drier.
[0044] As shown in FIGS. 2a and 2b, TEM and SEM analyses show that
particles of 20-50 nm having a uniform size and sphere form were
produced according to the method of the invention.
[0045] As shown in FIGS. 3 and 4, XRD analysis shows that the image
of pure copper crystalline without the image of impurities and
oxides was generated (Refer to FIG. 3). Further, thermogravimetric
analysis (TGA) shows that the organic content was about 4% (Refer
to FIG. 4).
[0046] Another aspect of the present invention may provide copper
nanoparticles and conductive ink including the copper nanoparticles
produced according to the invention.
[0047] That is, the copper particles of nano-size manufactured by
the method according to the present invention can be dispersed in
proper dispersion solution and then used in manufacturing
conductive nano ink. Thereafter, the nano ink can be used in
forming a metal pattern on a substrate or various electronic parts
using an ink jet technology.
[0048] Recently, demands for a metal patterning of a thin film
through ink jet or microwiring formation on a substrate have been
increased according to a tendency of miniaturization and high
densification of electronic parts.
[0049] In order to implement this, it is required that a conductive
ink should be made from copper particles of nano-size which shows
an excellent dispersibility, a uniform shape and a narrow
distribution of particle size.
[0050] The present invention provides a method of producing
nanoparticles massively meeting the requirements as well as being
simple and economical. Therefore, copper nanoparticles and a
conductive ink including the copper nanoparticles produced by the
method is included within the scope of the present invention.
[0051] Hereinafter, the present invention is described in further
detail by example. The following examples are intended to further
illustrate the present invention without limiting its scope.
EXAMPLE 1
Production of Copper Nanoparticles
[0052] 0.2 mole of sodium hypophosphates and 1 mole of PVP were
mixed with and dissolved into 400 ml of ethylene glycol in a beaker
with an agitator to prepare a first solution, and heated to
90.degree. C. 0.1 mole of a copper sulfate was dissolved into 100
ml of ethylene glycol to prepare a second solution and heated to
90.degree. C. The second solution was injected into the first
solution of 90.degree. C. at a time and the resulting solution was
strongly mixed with an agitator. After the solution turned into a
dark brown by a reduction reaction, cold distilled water was added,
cooled quickly and centrifuged to obtain copper nanoparticles of a
dark brown color. Then, the particles obtained were washed with
acetone and distilled water 3 times and dried for 3 hours in a
vacuum drier at 50.degree. C. to recover finally 12 g of copper
nanoparticles.
EXAMPLE 2
Production of Copper Nanoparticles
[0053] 1.6 mole of sodium hypophosphates and 4 mole of PVP were
mixed with and dissolved into 900 ml of ethylene glycol in a beaker
with an agitator to prepare a first solution, and heated to
90.degree. C. 0.4 mole of a copper sulfate was dissolved into 100
ml of ethylene glycol to prepare a second solution and heated to
90.degree. C. The second solution was injected into the first
solution at 90.degree. C. at a time and the resulting solution was
strongly mixed with an agitator. After the solution turned into a
dark brown by a reduction reaction, cold distilled water was added,
cooled quickly and centrifuged to obtain copper nanoparticles of a
dark brown color. Then, the particles obtained were washed with
acetone and distilled water 3 times and dried for 3 hours in a
vacuum drier at 50.degree. C. to finally recover 26 g of copper
nanoparticles.
[0054] It will be understood that various details of the presently
disclosed subject matter can be changed without departing from the
scope of the presently disclosed subject matter. Furthermore, the
foregoing description is for the purpose of illustration only, and
not for the purpose of limitation.
INDUSTRIAL APPLICABILITY
[0055] As described above, according to the present invention,
copper nanoparticles powder which are fine and uniform can be
produced simply, and thus the method is useful in mass production
of copper nanoparticles.
* * * * *